Affinity chromatography is used to perform isolation and purification by utilizing the affinity between a pair of substances having a specific interaction. For example, affinity chromatography is useful for purifying organic substances by distinguishing their biological property, or a specific chemical structure in the molecule.
An adsorbent for affinity chromatography (affinity gel) can be produced by binding combination groups (spacers) to an insoluble matrix to prepare an active support substance and then binding a ligand to the above spacer. Adsorption of a substance which specifically interacts with the ligand is performed by using this adsorbent.
Illustrative examples of a combination of such substance and a ligand are as follows.
Enzyme--Substrate, Product, Inhibitor, Co-Enzyme, Effector, PA1 Antigen--Antibody, PA1 Receptor--Agonist, PA1 Nucleic Acid--Base Pair, PA1 Lectin--Saccharose (Protein), PA1 Metal Chelate--Protein, PA1 Hydrophobic Group--Protein, PA1 Host--Guest.
In a separation or purification process or an analysis by the affinity chromatography, it is desired that the above active support substance which is the main component of the adsorbent have the following properties: (1) minimal nonspecific adsorption, (2) high porosity, (3) easily entering into combination with a great amount of the ligand, (4) adequate chemical stability under various conditions of pH, salt concentration and temperature, (5) no volume variation, (6) sufficient physical strength and stability, (7) high fluidity and (8) good resistance to biological contamination.
These desired properties are not always satisfied by conventional bases for affinity-chromatographic adsorbents such as cellulose, dextran, polyacrylamide and agarose. These typical materials are so-called soft gels having insufficient hardness and therefore have inferior fluidity and unfavorable separation characteristics which are vital disadvantages. They also have only a short life.
Silica beads which have been used recently have adequate hardness. However, since this material can not be used under alkaline conditions, use of this material greatly restricts the conditions for isolation, elution and washing.